A repository of geographic regions for Ruby
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This branch (master) is home to a rewrite of the Carmen library. If you're currently using Carmen in your application, you probably want to see the 0.2.x branch, which will be maintained until version 1 is ready.

If you'd like become a maintainer of the project, please let me know.

Carmen- A repository of geographic regions for Ruby

Build Status

A Little History

Carmen began its life as a replacement for Rails' country_select and state_select helpers. The API of the library was designed to facilitate a few view helpers and model validations, and that was about it.


It's been a few years since Carmen was released, and it has been used by a lot of projects. Many fine individuals have contributed code and data- I'm really happy with the way the community has improved the library. But this growth has brought to light many of the weaknesses in the current library and implementation.

I have decided that it is time to go back and rethink Carmen's data model and API, and in the process address some long standing issues. Carmen 1.0 will feature the following:

  • A new, cleaner API
  • Support for the old API via an optional require
  • More complete data via the iso-codes Debian package (idea borrowed from here)
  • A sane approach to internationalization, utilizing an existing i18n library.


  • Switch to a more complete data source (done)
  • Add the ability to overlay custom data on the dataset (done)
  • Rewrite spike-level V2 API implementation (working)
  • Provide a legacy api so existing users have an upgrade path: 'carmen/legacy'
  • Separate Rails view methods out into a carmen-rails gem (in progress)
  • i18n integration (working)

How to Use Carmen

Carmen is designed to make it easy to access Country and region data. You can query for a country by name or code:

require 'carmen'
include Carmen

us = Country.named('United States')
=> <#Carmen::Country name="United States">

A Country object has some attributes that may be useful:

=> 'US'

=> 'USA'

us.code # alias for alpha_2_code
=> 'US'

=> "United States of America"

A Country (and its subregions) can contain subregions. In the US these are states, but other countries have other types of regions:

=> true

  => <#Carmen::Region name="Alabama" type="state">

Country#subregions returns a RegionCollection, which can be queried similarly to a Country to find, for instance, a specific state:

illinois = us.subregions.coded('IL')
=> <#Carmen::Region "Illinois">

Subregions support a smaller set of attributes than countries:

  => "Illinois"

=> "IL"

=> "state"

Some subregions may contain additional subregions. An example of this is Spain:

spain = Country.named('Spain')
andalucia = spain.subregions.first
=> <#Carmen::Region name="Andalucía" type="autonomous community">

=> true

=> <#Carmen::Region name="Almería" type="province">

How Carmen organizes data

In order to facilitate support for I18n, Carmen stores the structure of regions seperately from the strings that represent a region's names. The defualt data that ships with Carmen is in the iso_data and locale directories, respectively.

Overriding structural data

You might want to tweak the data that Carmen provides for a variety of reasons. Carmen provides an overlay_path which can be set to point to a set of data that will be overlayed on top of the standard data. The structure of the files in this directory should mirror those in the data path that Carmen ships with.

To adda new country to the system, you would create a directory (let's use my_data as an example), and create a world.yml file inside it. Then set Carmen to use the new overlay path:

Carmen.overlay_path = File.expand_path('../my_data', __FILE___)

Elements within the data files are identified using their code values (or, in the case of countries, alpha_2_code). Create a new block for the country you wish to add inside my_data/world.yml:

- alpha_2_code: ZZ
  alpha_3_code: ZZZ
  numeric_code: "999"
  type: country

Now, modify the fields you wish to change, and delete the others. Be sure to specify alpha_2_code for countries and code for subregions, as those values are used internally by Carmen to match your customized data with the corresponding data in the default dataset.

Now, Carmen will reflect your personal view of the world:

=> "country"

You will also want to create a localization file with the names for the new region. See the section 'Customizing an existing locale', below.

Modifying existing elements

Existing regions can be modified by copying their existing data block into a new file at the correct overlay path, and modifying the values as desired.

Disabling elements

It is also possible to remove an element from the dataset by setting its _enabled value to anything YAML considers false, such as 'false' or 'no':

- alpha_2_code: EU
  _enabled: false

This will cause Carmen to not return that element from any query:

=> nil


Carmen ships with very simple I18n support. You can tell Carmen to use your own I18n backend:

Carmen.i18n_backend = YourI18nBackend.new

The object used as a backend must respond to t with a single argument (the key being looked up). This key will look something like en.world.us.il.name.

Setting the locale

If you use the built in I18n support, you can set the locale:

Carmen.i18n_backend.locale = :es

Each region is assigned a localization key based on the formula world.PARENT_CODE.CODE. The key used for the United States is world.us.

Customizing an existing locale

The library ships with a set of YAML files that contain localizations of many country names (and some states). If you want to override any of these values, create a YAML file that contains a nested hash structure, where each segment of the key is a hash:

      official_name: These Crazy States

This file can live anywhere, but it is recommended that it be stored in a structure similar to the one Carmen uses for its locale storage.

To tell Carmen to load this file, add the directory it is contained in to the set of locale paths used by the backend:


If you are using your own backend, then follow the steps necessary to have it load your additional files instead.